Chitinases exist widely in bacteria, fungi, plants, arthropods and vertebrates, and various studies of chitinases have been being made for the purpose of clarifying the meanings of their existence in such organisms and for applying them to industrial use.
On the other hand, for determining the activities of chitinases, known are a turbidimetric method, a method of measuring viscosity, a method of utilizing radioactivity and a method of quantifying reducing sugars, all of which are problematic in that they take much time and are troublesome.
With the development of glyco-chain engineering, a method of using a monose derivative having a p-nitrophenyl group at its reducing terminal to measure enzymatic activities has been developed, in which the activities of enzymes, especially those of exo-type ones are measured rapidly. However, no effective method has as yet been developed for measuring the activities of endo-type enzymes.
P-nitrophenyl derivatives of chitin-oligosaccharides which have been considered to be usable for the measurement of the activities of endo-type enzymes are problematic in that they are also substrates for exo-type enzymes capable of decomposing oligosaccharides successively from their end. Therefore, the development of substrates having a high specificity to endo-type enzymes is desired.
In practice, to identify endo-type or exo-type enzymes, employed is a complicated method of determining the reduction in the viscosity of the reaction system comprising an enzyme being reacted with a substrate. In this method, the viscosity of the reaction system comprising an endo-type enzyme being reacted with a substrate is rapidly lowered, while that of the reaction system comprising an exo-type enzyme being reacted with a substrate is slowly lowered.